But it wasn't until veteran World War I battlefield doctor and scientist Alexander Fleming discovered penicillin that physicians had a truly effective weapon against infectious disease. The chance contamination of a petri dish in Fleming's laboratory revolutionized medicine. After recognizing the antibacterial potential of penicillium notatum in 1928, Fleming published his findings in the British Journal of Experimental Pathology. Though the research was groundbreaking, mass production and purification of the compound was difficult, and research slow. It would take a second world war, two Oxford pathologists and American drug companies to make penicillin available to the masses.

Meanwhile, in 1932, German microbiologist Gerhard Domagk was earning his 1939 Nobel Prize. Domagk's discovery that prontosil rubrum, a derivative of sulphanilamide, was effective against lethal doses of staphylococci and haemolytic streptococci established sulfa drugs as the first synthetic antibacterials.